Electric lamp



March 13, 1962 E. H. WILEY ETAL ELECTRIC LAMP Filed June 16, 1958 Their- A ta-neg ELTTWQT G. Fw-idrich 3,025,42 Patented Mar. 13, 196.

fifice 3,025,424 ELECTRIC LAMP Emmett H. Wiley, Willowick, and Elmer G. Fridrich,

Cleveland, Ohio, assignors to General Electric Company, a corporation of New York Filed June 16, 1958, Ser. No. 744,305 2 Claims. (Cl. 313-115) This invention relates to lamps and, more particularly, to incandescent lamps useful in light projection devices.

Light projection systems have generally heretofore employed a reflector behind the light source of the system to redirect the back light to the projectors optical system. Such an arrangement requires an accurately formed, aligned and spaced geometric shape to redirect the back light. Further, if such a reflector is placed external'to the lamp envelope, it is subjected to oxidation and deterioration during use.

Placing a reflecting surface or baflle in close proximity to the incandescent filament coils of a high voltage projection lamp, that is, one operating on the normal household voltage of about 105 to 125 volts, presents certain problems. Such a baflle should be of refractory material as it must be able to withstand the incandescent heat of the filament coils. It was generally believed that placing a conducting material close to an incandescent coil having a high voltage potential across the portion of the coil in close proximity to the conducting material would cause the filament coil to are out due to reducing of the gap width between the two sides of the high voltage potential.

Further difficulty is experienced in projection lamps due to the blackening of the transparent lamp envelope as a result of gas and tungsten vapor emitted from the incandescent filament coils.

It is an object of the present invention to provide an improved projection lamp.

Another object of the present invention is to provide a projection lamp with an improved light redirecting baflle.

A further object of the present invention is to provide a projection lamp having improved baflle for minimizing blackening of the lamp envelope.

Briefly stated, according to the present invention, a reflecting shield or baflle of refractory material is placed in close proximity to the incandescent filament coils of a projection lamp, which has a high voltage impressed across the coils.

Such a baflle acts to direct light in a direction to increase the apparent brightness of the light source, that is, the spaces between the turns and segments of the filament coils are at least partially filled in with light, the effect of which is to increase the black body characteristic of the surface and to thereby increase the apparent brightness of the source. Such a baffle in close proximity to the incandescent coils requires no critical geometric shape or spacing in the optical system of the light projection device.

Other objects and advantages of the invention will appear to those skilled in the art from the following description and accompanying drawings, in which:

FIG. 1 is an elevation view, partly in section, of a projetcion lamp embodying the invention,

FIG. 2 is a partial side view, partly in section, of the projection lamp of FIG. 1,

FIG. 3 is a pictorial view, of a projection lamp embodying a modification according to the present invention,

FIG. 4 is a pictorial view of a projection lamp embodying a modification according to the "present invention,

FIG. 5 is a pictorial view of a projection lamp embod ing another modification according to the present invei tion,

FIG. 6 is a diagrammatic view illustrating the use of projection lamp accordance to the present invention in suitable optics system.

In the drawings, similar parts are designated by th same numbers; and the longitudinal lamp axis is desig nated by axis Y-Y, the light projection or optical axi of the lamp is designated by XX. It will be noted fror the drawings that the filament for a projection lamp, a conventionally built, may consist of a coiled coil fila ment as appears in FIGS. 1 and 5 and which consists o a coiled wire which, in turn, is coiled, thereby formin, several large turns or segments; or may be of the bi plane type, consisting of a series of straight segments 0 coiled wire, generally in two planes, as illustrated i1 FIGS. 3 and 4.

Referring to FIGS. 1 and 2, there is shown a high volt age projection lamp according to the instant invention which comprises a transparent vitreous envelope or bull 1 having an opaque coating 2 at one end and base 3 a the other end, and enclosing a mount shown generally a 4. The mount 4 comprises lead-in wires 5 and 6 sup porting a filament 7, herein shown having the form of coiled coil containing large turns or segments of COil8( wire. The filament may be of tungsten wire.

The lamp base 3 may be of any desired design, how ever, as herein illustrated, consists of a positioning ring 8 and a plurality of lead-in conductors 9, 10, 11 and 12 sealed through the lamp envelope. The lead-in support: 5, 6 are secured to the inner end of lead-in wires 10, 5 respectively. Lead-in wire 12 supports a baflle 13 it close proximity to the lamp filament, through bafile support 14. The baflie 13 must be of refractory material and may suitably be made of a conducting metal such as molybdenum or tungsten. The exact geometric shape and location from the filament of the baflle 13 is not critical; for the reasons that hereinafter appear, it is desirable, but not necessary, that the baflle 13 partially enclose the filament 7 particularly above the filament when the lamp is in its preferred operating position, as hereinafter explained, leaving uncovered the portion of the filament 7 which lies in the light projection axis XX of the lamp, FIG. 2 toward the projector optics system. The baflle 13, due to the cylindrical shape of the filament 7, takes on a generally semicircular or trough-shaped cross-section. The baffle may be constructed from .003 inch thick molybdenum sheet and placed within about /2 mm. of the coil. While the exact location of the baflle 13 is not critical, the beneficial results obtained from the baflle are diminished as the distance between the baflle and incandescent coil is lengthened. The location of the baflle from the incandescent coil depends somewhat on the coil diameter of the filament coils and the segment or turn spacing of the filament, and also on wattage of the lamp. For lamps up to about 1500 watts, the baffle may reasonably be placed between 1 and 3 coil diameters from the coil segments or turns.

By placing the bathe very near the light source in this manner, the source which is partially transparent between the turns and the segments of the fiarnent is made to appear brighter by filling in the open spaces with reflected light. By having the bafiie very near to the light source in this manner, the critical alignment and baffle shape is not needed. Further, since this baffle is inside the lamp, no glass transmission losses are encountered as with an external reflector. Also, compared to an internally mounted reflector placed further away and more accurately focused, this proximity baflle is cheaper to manufacture.

When the lamp is in its preferred operative position, as hereinafter explained, the bafile 13 may partially encircle and enclose the filament 7, thereby acting as a restriction to the natural flow of gas in an upward direction, preventing the cooling of the filament by convection currents and acting to collect tungsten vapors liberated by the filament so as to minimize the blackening of the bulb due to these vapors. Inasmuch as the incandescent filament is not as rapidly cooled when the proximity baffle restricts the flow of gas around the filament, the filament temperature can be maintained at a higher point with a lesser amount of power input than would otherwise be obtained. This is also due in part to the reflected power from the proximity baffle.

Another advantage is that the bafile is just slightly larger than the light source 5, thereby permitting utilization of the maximum source size and baflle image size to be projected to the optics system of the light projection apparatus.

Contrary to the popular belief that a conducting material placed so close to a coil having a high voltage impressed therethrough would so shorten the electrical path that an arc discharge would occur, the bafile according to the instant invention tends to suppress the occurrence of the are due to recombination of the ions in the conducting path, thereby inhibiting the occurrence of arc discharge.

While the lamp illustrated in FIGS. 1 and 2 may be burned with its longitudinal axis YY and its light axis XX in any desired position, the gas flow restricting effects of the bafile 13 are best when the lamp is burned with the baflle 13 partially covering the area above or below the filament 7, since, of course, the natural tendency of the gas stream in the lamp is to move upward in the vicinity of the hot filament. This baffling effect of the gases is therefore best obtained when the lamp is burned with its lonigtudinal axis YY in a vertical position while its light projection axis XX are horizontal; or while the longitudinal axis YY of the lamp is held horizontally and the light projection axis XX of the lamp is vertical. The gas baffling effect of the reflector 13 is a minimum when both the longitudinal lamp axis YY and the light projection axis XX are horizontal.

Referring to FIG. 3, there is shown a modification of the invention which is similar to that illustrated in FIGS. 1 and 2 except that the filament is of the biplane type. More specifically, the projection lamp includes the bulb 1 having an opaque coating 2 at one end and a base 3 at the other end enclosing a mount shown generally at 412. The mount 4a comprises lead-in wires 5a and 6a including a filament 7a of the biplane type. The filament coils 7a are supported by support wires 15, 16 fused into an upper bridge 17 and lower bridge 18, respectively, which in turn are secured to the lead-in conductors 5a, 6a through wires 19, 20, 21, and 22.

A baflle 13a, according to the instant invention, may be supported by two supporting wires 23, 24 which are fused into one of the bridges. The baffle 13a is, of course, made of suitable refractory metal. The exact geometric shape and location of the baffle 13a from the filament is not critical; the bafile takes on approximately the shape of the filament structure; therefore, as shown, it is of approximately rectangular shape. The baflle may be placed within about 2 mm. of the filament coil; however, the exact location of the bafiie 13a, as stated above, is not critical, but the beneficial results obtained from the baffle are diminished as the distance between the bafiie and the incandescent coil is lengthened.

It will be evident that the placing of the substantially flat reflecting baflle very near the light source in the manner described causes a virtual image of the filament to be formed behind the reflecting balfle the same distance as ,,the filament is in front of the baffie, and makes the light source appear brighter by filling in the open spaces between the turns and segments of the coil with reflected light.

Since the bafile 13a can function as a restriction to the natural flow of gas in an upward direction preventing the cooling of the filament by convection currents, the lamp illustrated in FIG. 3 is best burned with its light axis XX in a vertical direction, preferably with the light emitting in a downward direction. This has the further advantage that the light is transmitted through the bottom of the glass at a point where the tendency for the bulb to blacken is a minimum and the heat due to the incandescen-t filament is likewise a minimum thereby passing the light through a relatively cool portion of the lamp en-' velope and minimizing the tendency of local overheating in the envelope wall. This arrangement has the other advantages hereinbefore described in the discussion of the modification according to FIGS. 1 and 2.

Referring now to FIG. 4 there is illustrated a modification similar to FIG. 3 except that the bafile more nearly encircles and encloses the filament coils thereby producing the desired advantages to a-greater degree when burned in a proper position. The lamp as illustrated has a biplane filament 7b suspended from an upperand lower bridge 17b, 18b-respectively. The battle 13b is supported by two support wires 23b, 24b fused into one of the bridges 18b. The bafile 13b is of generally channel shape having its elements approximately parallel to the individual segments of the biplane filament, and consists of a center portion 25 and two end legs 26 and 27 at approximately right angles to the center portion 25. The end legs 26 and 27 are adjacent to the end segments of the filament 7b and the bafile 13b thereby partially encircles and encloses the filament 7b. In the lamp illustrated, small tongues 28, 29 were cut into the sides 26, 27 respectively of the baffle 13b and bent outwardly at the top so as to permit clearance between the bafiie 13b and supports 30, 31 which form the electrical connection between the filament 7b and the lead-in conductors 5b, 6b.

The battle 13b efliciently performs as a gas flow restriction when the lamp is burned with its light projection axis XX vertical, particularly when the light is projected in a downward direction through the bottom of the lamp envelope; and further performs effectively as a gas flow restriction when the lamp is burned with both the lamp longitudinal axis YY and the light projection axis XX in a horizontal position. The gas flow restricting effect of the baffle 13b is a minimum when the longitudinal lamp axis YY is vertical.

Referring now to FIG. 5 there is shown a coiled coil type projection lamp having an elliptical, non-axial reflector. The reflector and optics system are more fully described in copending application Serial No. 742,384 filed June 16, 1958 by Emmett H. Wiley, now Patent No. 2,904,714 granted September 15, 1959, and assigned to the assignee of the present invention. Briefly, however, the lamp consists of a coiled filament 70 supported by lead-in conductors 50, 6c, partially encircling or covering the filament 70. A bafile may be supported in place from support wire 32 secured to the inner end of lead-in wire 12. The bafile 130, due to the cylindrical shape of the filament 70 takes on a generally semicircular or trough-shaped cross-section. When the lamp shown in the embodiment of FIG. 5 is mounted with its longitudinal axis YY vertically, the baflle 13c partially encircles and encloses the filament 70 at its top, acting as a restriction to the natural flow of gas in an upward direction around the filament and preventing the cooling of the filament by the convection current, and further acting to collect tungsten vapors liberated by the filament thereby minimizing the blackening of the bulb due to the vapors. In this position the light from the filament 70 as well as the light from the baffle 130, is projected downwardly onto the elliptical reflector 33 which then reflects the light horizontally along the light axis XX. As more fully described in the above mentioned co-pending application,

such an arrangement has the further advantage that the light is transmitted through the portion of the bulb which does not collect tungsten vapor gas and which is not excessively heated by hot convection currents.

A typical optics system which can utilize the modifications of FIGS. 1 through 4 is illustrated in FIG. 6. In this figure, an incandescent projection lamp 34 according to the present invention is used as the light source and consists essentially of a sealed glass envelope 35 containing an incandescent biplane filament 36 and a proximity bafiie 37 according to the present invention. The light from the lamp 34 passes through a condensing lens 38, through a transparent film 39 at the film gate 40 and into the objective lens 41 of the projector. While possessing all the desirable advantages hereinbefore enumerated, such an optics system has the further advantage of eliminating the need for a back reflector 42 (shown dotted) of geometric design and accurately located in the optical system.

J While many modifications will occur to those skilled in the art, for example, the bafiies 13a, 13b in the biplane lamps may be supported on support wires secured to leadin wires, the invention is to be limited only by the claims annexed to and forming a part of this specification.

What we claim as new and desire to secure by Letters Patent of the United States is:

l. A high voltage incandescent projection lamp comprising a sealed light-transmitting envelope, a biplane filament in said envelope operable at a voltage in excess of about 100 volts and comprising a plurality of spaced parallel segments of coiled wire arranged adjacent a common plane within a substantially rectangular outline, am a substantially flat, imperforate, refractory sheet meta reflector having a peripheral outline of the same ordei of size as said filament and located behind and in close proximity to said filament in a plane parallel to said common plane, said reflector being electrically insulated frorr said filament and being spaced therefrom a distance 01 approximately two millimeters corresponding to between one and three coil diameters of the coiled segments 01 said filament whereby a virtual image of the filament is formed behind the reflector and the spaces between said filament segments are filled in with reflected light.

2. A lamp as set forth in claim 1 wherein said reflector is provided with leg portions adjacent to the end segments of the filament partially encircling and enclosing said filament.

References Cited in the file of this patent UNITED STATES PATENTS 1,646,442 Brizendine Oct. 25, 1927 1,793,398 Hamberger Feb. 17, 1931 1,947,243 Born Feb. 13, 1934 2,060,584 McIlvaine Nov. 10, 1936 2,467,710 Van Horn et al. Apr. 19, 1949 2,617,062 Rijnders Nov. 4, 1952 2,912,610 Verbeek Nov. 10, 1959 FOREIGN PATENTS 1,091,341 France Apr. 12, 1955 525,671 Canada May 29, 1956 

